Pressure responsive device



Oct. 27, 1964 R. .1. REILLY PRESSURE RESPONSIVE DEVICE Filed July 20, 1962 mQEDOm mm3wmmmm 0404 ombqmwaO mmDwmmmm FNVENTOR. ZJCHA D J FUZZY 3,153,934 PRESSURE RESPGNSTVE DEVECE Richard .1. Reilly, St. Paul, Minn, assignor to Honeywell 1111s., a corporation oi Delaware Filed an 20, 1962, Set. No. 211,340 4 Claims. ((11. 73-388) The present invention is directed to a unique type of pressure responsive amplifier, and more particularly is directed to a pressure responsive device that utilizes a pure fluid amplifier as a means of sensing a pressure change from any type of fluid pressure source.

The use of pure fluid amplifiers to perform various functions has increased steadily since the original introduction of the fluid amplifier concept. A general discussion of fluid amplifier concepts and construction can be found in the literature and in numerous recently issued patents. Two recently issued patents by two of the three original inventors of the pure fluid amplifier contain detailed descriptions of various types of amplifiers and their modes of operation. These patents are the Warren Patent No. 3,001,698 issued September 26, 1961, and the Horton Patent No. 3,024,805 issued on March 13, 1962. Additional information on another type of fluid amplifier can be found in the Reilly Patent No. 3,030,979 issued on April 24, 1962.

With the large number of variations in configuration and operating details of dilferent types of fluid amplifiers, it becomes apparent that this field encompasses many variations of specific design, but that a single basic concept is encompassed. This basic concept is the idea of providing a means of switching a fluid floW from one path or channel to a second path or channel without the utilization of any moving parts in the immediate switching area. This difiers from a conventional valve in a substantial manner and therefore lends itself to utilization in many unique types of switching or amplifying functions. The present invention recognizes these advantages of a pure fluid amplifier, and further recognizes a new Way to use the fluid amplifier as a pressure responsive device.

It is the primary object of the present invention to disclose a fluid pressure responsive device that responds to a change in pressure that is not a fixed percent of the applied pressure.

It is a further object of the present invention to disclose a pressure responsive device that can indicate very small pressure changes in any type or level of pressure source.

Yet another object of the present invention is to disclose a pressure responsive device that contains no moving parts, whatsoever.

A still further object of the present invention is to disclose a pressure responsive device that can be used with any type of fluid, where the term fluid means any type of gas, liquid, mixture of gas and liquid, and mixtures of any other types which can be caused to move under a pressure diflerential.

These and other objects will become apparent when the single drawing is considered along with a detailed discussion of the construction of the pressure responsive device and its mode of operation.

The single drawing in the present application discloses, in substantially schematic form, a pressure responsive device utilizing a fluid amplifier as the pressure responsive section of the device. In the drawing, a source of pressure is provided that supplies fluid under pressure to pipe 11. The pipe 11 has a T 12 that in turn supplies fluid to pipes 13 and 14. The pipe 13 supplies pressure from the source 10 to any type of pressure operated or utilizing load 19. The pipe 14 supplies fluid from the pressure source 10 to the pressure responsive device generally shown at 15.

The pressure responsive device 15 includes an inlet means 16 in the form of a channel or pipe that has a reduced cross-section or input at 17 to provide a jet or stream of fluid flow in a conventional fashion for a fluid amplifier. Also connected to the input means 16 is a pipe 20, containing an adjustable restriction 20', that is connected to a control inlet means or control port 21 that is capable of issuing a jet of fluid substantially at right angles to any fluid flow from the input 17. The adjustable restriction 20' could be in the form of a needle valve. The fluid flows from both 17 and 21 generally into an output means 22 that is made up of a pair of output channels 23 and 24. It Will be noted that the opening 17 is generally directed into the output channel 24 so that the normal fluid flow from the input means 16 is directly into the output channel 2 1. This provides a mechanically biased fluid amplifier. Other means of biasing fluid amplifiers are well known in the fluid amplifier art. These means are by the addition of various jets and mechanical structures and will not be described as they would lend little to the simplified discussion of the present device.

The output channels 23 and 24 separate in a diverging fashion to form two legs of what would normally be a fluid amplifier. The output channels 23 and 24 however are terminated in a common pipe 25 that joins the ends 26 and 27 of the channels 23 and 24 together. The common section (or pipe 25, has an outlet 29 that leads to a throttling means 28 in the form of a throttling or reduction type of valve.

Projecting through a wall 30 of the output channel 23, through a pair of insulators 31 and 32, is a pair of wires connected to a thermistor 33. The thermistor 33 is any type of resistor which changes in resistance valve substantially upon a change of temperature of its own material. Thermistors are well known in the electrical arts and it is believed that further discussion of the thermistors characteristics are unnecessary. The thermistor 33 is connected by conductor 34 to a power source 35, shown as a battery. The battery 35 is then connected through a variable resistance 36 to conductor 37 and a current indicating or control device 40. The device 40 is in turn connected by conductor 41 back to the thermistor 33 to complete an electric circuit. The operation of the just described circuit will be incorporated below.

Operation In operating the present pressure responsive device, the pressure source 10 is energized to supply a fluid pressure to any convenient load 19 from pipe 13. At the same time, a fluid flow fills the pressure responsive device 15 by flowing through the pipe 14 into the input means 16. A fluid flow will then issue from the ports 17 and 21. A flow will in turn fill the entire unit by filling the output means 22, the channels 23 and 24, the output connecting pipes 25 and 29. The throttling valve 28 is adjusted to reduce the flow of fluid through the device to a low level. As soon as the unit has been filled and adjusted to a low level of flow, two jets of fluid will be issuing into the output means 22. The valves 20' and 28 are adjusted so that the jet issuing from 17 is sufliciently strong enough to pass directly into the output channel 24 even through a slight flow of fluid is impinging on its side from the port 21. This type of bias arrangement provides that a flow of fluid will issue from the input means 16 to the output channel 24 and thence through the pipe 29 and the valve 28 to a low pressure area, such as the atmosphere, or the fluid can be returned to the low pressure side of the pressure source 10. As

3 long as the flow from the input means 16 is biased into the output channel 24, the device is considered to be in its normal or standby condition.

If a pressure increase occurs in the source 10, the flow of fluid from the input port 17 and the control inletmeans or control port 21 increases. The flow from control port 21 then issues in sufficient amount to dislodge the biased state of the device and switches the fluid flow into channel 23. This switching operation is well known in the fluid amplifier art and will not be discussed in further detail. The switch of fluid flow to channel 23 occurs with an increase in the source pressure from and causes the fluid to flow by the thermistor 33. The flow of fluid by the thermistor 33 tends to cool the thermistor 33 beyond that which occurred when the fluid around the thermistor was standing still or moving in a very slight fashion when the main flow was flowing through the outlet channel 24. The shift of fluid from channel 24 to channel 23 therefore affects the resistance of the thermistor 33 by cooling it. The circuit connected to the thermistor 33, which includes the battery 35, the resistor 36, and the current indicating or control device 40 then has a change in current flow. Since the battery remains constant, the resistor 36 remains constant, and the resistance of the current indicating device 40 remains constant, any change in resistance of the thermistor 33 is reflected as a change in current. The current indicating device 40 then is capable of indicating the change in fluid flow between channels 24 and 23. The control device 40 further could be connected to any appropriate circuitry as would be well known to one skilled in the art. It should also be noted that the extreme sensitivity of the device is in no way concerned with the resolution of the thermistor. The sensitivity is a function of the fluid phenomena and the thermistor merely determines the gross state of the device. By way of specific example, the current responsive device 40 could be a meter movement indicating current flow or could be a meter movement type of relay for switching purposes to control a circuit upon a change in pressure of the source it).

If the pressure at source 10 returns to its normal level, the fluid issuing from the input port 17 again overcomes the side force of the flow from the control inlet port 21 and the fluid switches back to channel 24. As soon as the fluid switches back to channel 24, the thermistor 33 changes its heating characteristics again as it is no longer being cooled by the flow of fluid and the indicating device 40 then responds.

' By proper arrangement of the channels in the present device, the pressure responsive device can sense either increases or decreases in pressure. This can be accomplished by moving the thermistor from the leg 23 to the leg 24 and operating the device with the valves and 28 set so that the normal flow is in channel 23 as opposed to channel 24. In this case, a reduction of pressure would allow the biased amplifier to switch to channel 24 and the sensing function of the thermistor 33 would be utilized.

The present device has a very unique characteristic in that the unit is capable of sensing a slight change in pressure that is not a percentage of the applied pressure. A specific example may bring out the importance of this feature. If the pressure source 10 were, for examples sake, 10,000 psi, a 1% change in pressure would be 100 psi. A 100 p.s.i. pressure change is a substantial pressure change and would be difficult to read on a gauge that was suitable of withstanding a 10,000 psi differential pressure. With the present device, a low pressure can be sensed regardless of the ambient merely by adjusting the throttling valve 20 and 28 so that the flow through the unit is as close to the switching point as is desired for the particular pressure diiferential to be sensed. The present device can also be used on relatively low pressures and again senses a differential pressure and not a percent of the applied pressure. Experimental tests run 4 on this type of a pressure responsive device have shown that a differential pressure of 0.01 inch of water across the device, as set by the throttling valve 23, has allowed sensing of changes in the supply line pressure in the order of 2 10 p.s.i.g. It will be noted that an exceedingly sensitive device is thus disclosed where it is possible to sense a pressure change in the order of 0.00002 p.s.i.g. with an ambient of 0.01 inch of water differential applied to the unit. This test data has shown that the unit is sensitive to a diflerential pressure and not a percentage function of the pressure level of the operating system.

In constructing a system disclosed in the present application, any convenient fluid amplifier structure can be utilized. The concept also envisions any type of flow sensing device for sensing the shift of the amplifier upon a change of applied pressure. An example of a pressure responsive device other than the thermistor 33 would be such as a diaphragm pressure gauge, a pendulous device, or any other type of flow sensitive unit that could be embedded in channel 23 and that would be responsive to the change from substantially no flow to low flow conditions existing with the throttling valve adjusted. Since it is obvious that many changes could be made in the specific physical configuration disclosed in the present application of the preferred embodiment of the device, the applicant wishes to be limited in the scope of his invention only by the scope of the appended claims.

I claim as my invention:

1. A pressure responsive device, including; fluid amplifier means having input means connected to a source of fluid under pressure, and output means having at least two output channels; throttling means partially closing said output means to allow a normal continuous fluid flow through said device; control inlet means connected to said fluid source and effective to switch said fluid in said amplifier means between said channels upon a predetermined change in pressure being applied to said amplifier means; said output means including flow sensing means to detect said switching of said fluid between said output channels with said normal fluid flow occurring in a first of said channels and said throttling means; and said control inlet means having a changing fluid flow to cause said normal fluid flow to switch to a second of said channels to activate said flow sensing means upon said predetermined change in pressure to said device.

2. A pressure responsive device, including: biased fluid amplifier means having input means connected to a source of fluid under pressure, and output means having at least two output channels; throttling means partially closing said output means to establish a relatively low rate of continuous fluid flow through said device; control inlet means connected to said source of fluid and directed to switch said fluid in said amplifier means from a first of said channels to a second of said channels upon a predetermined change in pressure to said amplifier means; and said second channel including flow sensing means to detect said switching of said fluid between said channels; said fluid normally flowing in said first channel and said throttling means when the flow of fluid from said control inlet means is insufficient to switch said amplifier means; said control inlet means issuing a changing fluid flow to switch said continuous fluid flow to said second channel to activate said flow sensing means upon the occurrence of said predetermined change i pressure to said device. 7

3. A pressure responsive device, including: a biased fluid amplifier having an inlet connected to a source of fluid under pressure, and an output means having two output channels; said inlet directed at a first of said output channels to allow said fluid to normally be directed into said first channel; a throttling valve partially closing both of the output channels to establish a relatively low rate of continuous fluid flow through said device; a control port connected to said inlet and directed to switch said fluid in said output means from the first of said channels to a second of said channels; and said second channel including flow sensing means to detect said switching of said fluid between said output channels; said fluid normally flowing in said first channel and said throttling valve when the flow of fluid from said control port is insufficient to switch said amplifier; said control port issuing a fluid flow to switch said continuous fluid flow to said second channel to activate said flow sensing means upon a predetermined rise in pressure to said device.

4. A pressure responsive device, including: a biased fluid amplifier having an inlet connected to a source of fluid under pressure, and an output means having two output channels; said inlet directed at a first of said out put channels to allow said fluid to normally be directed into said first channel; a throttling valve partially closing both of the output channels to establish a relatively low rate of continuous fluid flow through said device; a control port connected to said inlet and directed to switch said fluid in said output means from the first of said channels to a second of said channels; and said second channel including a thermistor and external circuit means to detect said switching of said fluid between said output channels; said fluid normally flowing in said first channel and said throttling valve when the flow of fluid from said control port is insufiicient to switch said amplifier; said control port issuing a fluid flow to switch said continuous fluid flow to said second channel to cool said thermistor to activate said external circuit means upon a predetermined rise in pressure to said device.

References Cited in the file of this patent UNITED STATES PATENTS 2,707,021 Harris Apr. 26, 1955 2,892,347 Laprand June 30, 1959 2,973,001 McAuley Feb. 28, 1961 3,001,539 Hurvitz Sept. 26, 1961 

1. A PRESSURE RESPONSIVE DEVICE, INCLUDING; FLUID AMPLIFIER MEANS HAVING INPUT MEANS CONNECTED TO A SOURCE OF FLUID UNDER PRESSURE, AND OUTPUT MEANS HAVING AT LEAST TWO OUTPUT CHANNELS; THROTTLING MEANS PARTIALLY CLOSING SAID OUTPUT MEANS TO ALLOW A NORMAL CONTINUOUS FLUID FLOW THROUGH SAID DEVICE; CONTROL INLET MEANS CONNECTED TO SAID FLUID SOURCE AND EFFECTIVE TO SWITCH SAID FLUID IN SAID AMPLIFIER MEANS BETWEEN SAID CHANNELS UPON A PREDETERMINED CHANGE IN PRESSURE BEING APPLIED TO SAID AMPLIFIER MEANS; SAID OUTPUT MEANS INCLUDING FLOW SENSING MEANS TO DETECT SAID SWITCHING OF SAID FLUID BETWEEN SAID OUTPUT CHANNELS WITH SAID NORMAL FLUID FLOW OCCURRING IN A FIRST OF SAID CHANNELS AND SAID THROTTLING MEANS; AND SAID CONTROL INLET MEANS HAVING A CHANGING FLUID FLOW TO CAUSE SAID NORMAL FLUID FLOW TO SWITCH TO A SECOND OF SAID CHANNELS TO ACTIVATE SAID FLOW SENSING MEANS UPON SAID PREDETERMINED CHANGE IN PRESSURE TO SAID DEVICE. 